Topic: Parents' knowledge and opinion on vaccination for pre-school children Research objectives: to look into parents' knowledge and opinion on vaccination for pre-school children. Draft study: a cross-sectional study conducted in June 2016 in the kindergartens of the Center for Preschool Education in Osijek. Participants and methods: The research included 250 participants of which 60 were male and 190 female. Anonymous questionnaire made of 18 questions was used. Results: Most participants were between 30 and 39 years of age. Regardless of their qualifications, parents had positive opinion on vaccines, vaccination and their effectiveness, and they did not consider them dangerous for their children's health. Nevertheless, parents who have completed only primary education (NSS) have more positive opinion towards vaccination than parents with completed secondary education (SSS) and parents with a college/university degree (VŠS/VSS). Positive opinion on vaccines and vaccination increases in accordance with parents' socioeconomic status. Paediatrician is the most reliable source of information, followed by a doctor of school medicine. Parents who have one child have the same opinion as parents with three or more children. Almost 2/3 of participants, regardless of their level of education, do not know if there is a correlation between vaccination and autism. Regardless of their level of education all parents have about the same knowledge of importance of herd immunity. They know that the side effects of vaccination are more acceptable than effects of illnesses (infections) against which vaccination is taken, but they are wrong to think that vaccines cause temporary loss of immunity. Conclusion: Although parents' opinions on vaccines and vaccination are mostly positive and their knowledge on the topic satisfactory, it is necessary to continue to educate them, in order to preserve awareness of the need for vaccination and to stop consequences of negative campaign.